In recent years, rechargeable electric storage devices including battery cells such as lithium ion battery cells and nickel hydrogen battery cells, and capacitors such as electric double layer capacitors are employed as a power source for vehicles such as cars and motorcycles, and various equipment such as mobile terminals, notebook computers, etc. Such an electric storage device, for example, is disclosed in JP 2007-265666 A.
With an object of providing a non-aqueous electrolyte secondary battery cell that exhibits excellent load characteristics and cycle characteristics, using a separator that is less likely to clog, even after charge/discharge cycle is repeated, JP 2007-265666 A discloses a non-aqueous electrolyte secondary battery cell in which a separator, which is supposed to have a compressibility of 20%, has a compression resistance of 100 sec/μm or less on the membrane thickness basis. JP 2007-265666 A also discloses that the compressibility of the separator is defined as: (membrane thickness of separator before compression−membrane thickness of separator after compression)/membrane thickness of separator before compression×100, and the compression resistance of the separator is defined as (air resistance of separator after compression−air resistance of separator before compression)/(membrane thickness of separator before compression−membrane thickness of separator after compression)×100. The non-aqueous electrolyte secondary battery cell of JP 2007-265666 A uses a separator with excellent compression resistance, and therefore even when the separator is compressed due to swelling of the positive electrode and the negative electrode as the charge/discharge cycle proceeds, the air resistance of the separator is less likely to increase, so that the separator is less likely to clog. Therefore, the ion conductivity of the separator is less likely to decrease, which enables the above-mentioned object to be achieved.